Modern train brake control systems typically use a central controller to control the brakes of the rail vehicles that comprise the train. A train operator located in the lead locomotive manipulates the brake handles of the train to apply and release the brakes of the trucks on each rail vehicle as desired. The inputs from the brake handles are typically processed by a cab control unit and passed to the central controller. In response to these and other inputs, the central controller sends a brake command signal to each of the rail vehicles along a pneumatic or an electrical trainline or both. The brake command signal can be the carrier of a request for service braking or one for emergency braking or even both. Brake equipment on each rail vehicle applies or releases the brakes according to the dictates of the particular brake command signal received.
Depending on the type of brake control system, the service and emergency braking requests may be carried on the same or separate pneumatic trainlines. In the WABCO 26-C Brake Control System, the brake pipe is used to convey both the service and emergency braking requests. In the WABCO RT-2 Brake Control System, the straight air pipe conveys the service braking requests while the brake pipe carries the emergency braking requests.
The brake equipment on each rail vehicle may include either exclusively pneumatic equipment or a combination of electrical and pneumatic (i.e., electropneumatic) equipment. In those rail vehicles featuring only pneumatic brake equipment, the central controller sends the brake command signal along a pneumatic trainline to each rail vehicle. The pneumatic brake equipment on each rail vehicle responds pneumatically to apply or release the brakes according to the dictates of the pneumatic brake command signal. In those rail vehicles featuring electropneumatic brake equipment, each rail vehicle typically includes a master electronic unit (MEU) whose construction and operation are generally well known in the brake control art. The central controller sends the brake command signal to each rail vehicle along either a pneumatic or an electrical trainline or both.
The MEU on each rail vehicle receives this brake command signal and various other signals in response to which it directly controls the electropneumatic equipment according to principles well known in the brake control art. Specifically, the MEU generates the electrical signals which directly open or close the various valves of the prior art electropneumatic equipment which supply pressure to or vent pressure from the brake cylinders. The brakes of all the trucks on the rail vehicle apply and release accordingly.
The exclusively pneumatic equipment and the electropneumatic equipment of the prior art brake control systems discussed previously have certain disadvantages when compared to the inventions set forth below and in related applications. Such prior art equipment typically provides service braking, emergency braking and wheel slip and spin control functions from separate components. This requires a lot of space. Moreover, each component in these prior art systems is typically physically separated from the electronics that controls it. Large amounts of wiring are therefore required to interconnect each component and its controlling electronics. Each rail vehicle, of course, bears the weight of this wiring.
It would therefore be highly desirable to have brake equipment in which service braking and emergency braking functions and, if desired, wheel slip and spin control functions can be consolidated along with their associated electronics within a single, and comparatively small, package. The amount of wiring that would be required to interconnect the various electropneumatic components and their associated electronics in each package would be significantly reduced as compared to the prior art equipment. This would reduce the weight that each rail vehicle would be required to bear. The single enclosure for each of the components and their associated electronics would also afford better protection from adverse environmental conditions.
It would also be highly desirable to control the brakes at the truck level. In those prior art systems featuring only pneumatic brake equipment on each rail vehicle, the brakes are controlled only at the rail vehicle or train level. Similarly, in those prior art brake control systems featuring electropneumatic brake equipment on each rail vehicle, the MEU is used to control the brakes only at the rail vehicle level. By controlling the brakes at each truck individually, this would allow for better overall control of the brakes given the inevitable variations in load weight, motion, wheel slippage and other factors affecting each rail vehicle.
It would also be highly desirable to design such a package that either by itself or in conjunction with one or more other novel devices can be used within and made a part of a variety of train brake control systems such as those used to control passenger trains, subway trains and trolleys.
It should be noted that the foregoing background information is provided to assist the reader in understanding the present invention. Accordingly, any terms of art used herein are not intended to be limited to any particular narrow interpretation unless specifically stated otherwise in this document.